The activity of a polymerase can be improved by joining a sequence-non-specific double-stranded nucleic acid binding domain to the enzyme, or its catalytic domain (see, e.g., WO0192501). Such modified polymerases exhibit increased processivity in comparison to the unmodified enzymes. In some instances, however, it may be useful to additionally modify the processivity of these improved polymerases. For example, when performing polymerase chain reactions (PCR) for long templates, the use of highly processive polymerases often results in lower yields. Therefore, there is a need to modulate polymerase processivity to optimize the enzyme for specific purposes, e.g., long PCR.
Further, polymerase modification with a sequence-non-specific double-stranded nucleic acid binding domain may, in some cases, decrease polymerase discrimination between mismatched primer/templates and properly matched primer/template. Therefore, there can also be a need to increase the specificity of a polymerase for the primer template.
The current invention addresses both of these needs, i.e., the need for modulating processivity and primer/template binding specificity. The invention provides a polymerase conjugate comprising a mutated DNA binding domain such as Sso7d, Sac7d, or related domains joined to the polymerase or catalytic domain of the polymerase. The mutated binding domain comprises one or more amino acid substitutions at a face residue of the DNA binding domain polypeptide sequence. These substituted fusion polymerases exhibit enhanced performance capabilities in polymerase reactions, e.g., a polymerase chain reaction (PCR).